1. Field of the Invention
The present invention relates generally to clay stabilizing agents useful in subterranean formation treating, and more particularly, to the preparation and use of a water soluble clay stabilizing agent.
2. Description of the Prior Art
The production of hydrocarbons from subterranean formations is often troubled by the presence of clays and other fines, which can migrate with produced fluids and plug off or restrict the flow of such fluids. The migration of fines in a subterranean formation is generally the result of clay swelling and/or the disturbance of normally quiescent fines by the introduction of water foreign to the formation therein. Typically, the foreign water is introduced into the formation in completing and/or treating the formation to stimulate production of hydrocarbons therefrom such as fracturing, acidizing and other treatments utilizing aqueous fluids.
A variety of clay stabilizing agents have been developed and used heretofore to control the ill effects of water on clay and/or other fines in subterranean formations containing hydrocarbons. For example, inorganic polycationic polymers or complexes have been utilized as clay stabilizing agents. Ions contained in the clay are replaced by the inorganic polycationic polymers or complexes thereby transforming the clays into relatively non-swelling forms. Such inorganic polycationic polymers or complexes have been successful in controlling swelling clays, but have various limitations. For example, two commonly used inorganic polycationic polymers are zirconyl chloride (ZrOCl.sub.2) and aluminum hydroxychloride (Al(OH).sub.x Cl.sub.y). Aluminum hydroxychloride requires a cure time after it is placed in the presence of the clay. Also, aluminum hydroxychloride can tolerate only a limited amount of carbonate material in the formation and is removed by contact with acids such as when a subsequent acid treatment of the formation is necessary. Zirconyl chloride is limited in the pH range of the placement fluid and can also be removed by acid under certain conditions.
Organic polycationic polymers have also been utilized for stabilizing clays or migrating fines or combinations thereof. For example, U.S. Pat. Nos. 4,336,071; 4,366,072; 4,366,073; 4,366,074; 4,374,739; 4,460,483; and 4,462,718, all assigned to the assignee of this present invention, disclose the use of organic polycationic polymers as clay stabilizing agents. U.S. Pat. Nos. 4,497,596 and 4,536,305, also assigned to the assignee of this invention, disclose water soluble organic polycationic polymers containing two or three quaternary ammonium moieties in the monomer repeat units.
Organic cationic polymers have achieved great success as clay stabilizing agents in that they are effective when dissolved in aqueous treating fluids in small concentrations, they resist removal by most subsequent acid and other treatments and result in long life stabilization of formation clays and fines. However, all of the heretofore used organic cationic polymers are hygroscopic and are available for use only as dilute aqueous solutions. Thus, there is a need for a highly effective clay stabilizing agent which can be prepared and used as a concentrated aqueous solution or a non-hygroscopic solid which can be readily dissolved in aqueous fluids.
By the present invention, methods of preparing a concentrated aqueous solution of a highly effective clay stabilizing agent or such agent in a solid non-hygroscopic form are provided as well as methods of using such agent for reducing clay swelling and fines migration in subterranean formations.